Impact resistant wall design and building built using the same

ABSTRACT

A saferoom/tornado shelter is made primarily of wood and includes walls that can withstand missile impact testing as recommended under Federal guidance and regulations. The saferooms of the present invention can be designed for a single family or small business, or can be designed as a larger community shelter. The wood wall can accommodate various architectural finish treatments and enhancements much more easily than a concrete or steel building saferoom. The walls can be made from dimensional lumber, stacked along its width and the saferooms can be assembled without the need for glue, wood screws or the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patent application No. 61/694,749, filed Aug. 29, 2012, the contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to wall designs and secure structures and more particularly, to a wall design that is impact resistant and a building built using such a wall design to provide shelter during storms, such as tornados.

Tornados can strike with little warning. People are often told to find an interior room and stay in a doorway or inside a bathtub, or some similar protective area.

Tornado shelters can be built to protect a single family or a group or community. The Federal Emergency Management Agency (FEMA) provides regulations for saferooms to survive tornados. FEMA P-320/P-361 provide design requirements for any such saferoom, whether located underground, attached to a home, in a basement, or as a separate structure.

Having a saferoom for a home or small business can help provide “near-absolute protection” from injury or death caused by the dangerous forces of extreme winds. Near-absolute protection means that, based on FEMA's current knowledge of tornadoes and hurricanes, there is a very high probability that the occupants of a saferoom built according to FEMA's guidance will avoid injury or death. A saferoom can also relieve some of the anxiety created by the threat of an incoming tornado or hurricane.

Typical stand-alone saferooms are not very aesthetically pleasing most being precast concrete construction or steel panel boxes, entirely focused on functionality as a refuge with little focus on pleasing design.

As can be seen, there is a need for an improved design for saferooms that can provide proper protection under FEMA P-320/P-361, while providing an aesthetically pleasing design that can be easily assembled on site.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a wall assembly comprises a plurality pieces of lumber having a length, a width and a thickness, the plurality pieces of lumber stacked atop each other to form a wall height equal to a sum of the thickness of each of the plurality of pieces of lumber; a first channel formed along the length of the lumber, the first channel formed in a first side of the lumber proximate to an outer surface of the wall; a second channel formed along the length of the lumber, the second channel formed in a second, opposite side of the lumber proximate a central region of the lumber, wherein the first and second channels of one of the plurality of pieces of lumber aligns with the first and second channels of an adjacent one of the plurality pieces of lumber; first and second spline members fitting into the first and second channels; a top plate on a top edge of the wall; a truss rod fitting through the top plate, passing through the wall, and secured to a floor plate, wherein the truss rod fits through the wall proximate an inner surface of the wall; and a tensioning device disposed at an end of the truss rod, the tensioning device operable to apply tension on the top plate and the plurality of pieces of lumber disposed therebelow.

In another aspect of the present invention, a saferoom comprises a roof; and a plurality of walls, each of the plurality of walls comprising a plurality pieces of lumber having a length, a width and a thickness, the plurality pieces of lumber stacked atop each other to form a wall height equal to a sum of the thickness of each of the plurality of pieces of lumber; a first channel formed along the length of the lumber, the first channel formed in a first side of the lumber proximate to an outer surface of the wall; a second channel formed along the length of the lumber, the second channel formed in a second, opposite side of the lumber proximate a central region of the lumber, wherein the first and second channels of one of the plurality of pieces of lumber aligns with the first and second channels of an adjacent one of the plurality pieces of lumber; first and second spline members fitting into the first and second channels; a top plate on a top edge of the wall; a truss rod fitting through the top plate, passing through the wall, and secured to a floor plate, wherein the truss rod fits through the wall proximate an inner surface of the wall; and a tensioning device disposed at an end of the truss rod, the tensioning device operable to apply tension on the top plate and the plurality of pieces of lumber disposed therebelow.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a saferoom according to an exemplary embodiment of the present invention;

FIG. 2 is a front view of the saferoom of FIG. 1;

FIG. 3 is an end perspective view of a test portion of a wall design, after being struck by a projectile, according to an exemplary embodiment of the present invention;

FIG. 4 is another end view of the test wall design of FIG. 3;

FIG. 5 is an end perspective view of the test wall portion of FIG. 3, showing multiple projectile strikes;

FIG. 6 is a back side (interior) view of the test wall portion of FIG. 5, showing no interior wall disturbance after multiple projectile strikes;

FIG. 7 is a front perspective view of the test wall portion of FIG. 5;

FIG. 8 is a cross-sectional view taken along line S1 of FIG. 2;

FIG. 9 is a detail view taken along view D-1 of FIG. 8;

FIG. 10 is a detail view taken along view D-2 of FIG. 8;

FIG. 11 is a detail view taken along view D-3 of FIG. 8;

FIG. 12 is a detail view taken along view D-4 of FIG. 8;

FIG. 13 is a detail view taken along view D-5 of FIG. 8;

FIG. 14 is a detail view taken along view D-6 of FIG. 8;

FIG. 15 is a detail view taken along view D-7 of FIG. 8;

FIG. 16 is a top view of the saferoom of FIG. 1;

FIG. 17 is a cross-sectional view taken along line S2 of FIG. 2;

FIG. 18 is a detail view taken along view C-1 of FIG. 16;

FIG. 19 is a detail view taken along view C-2 of FIG. 16;

FIG. 20 is a detail view taken along view C-3 of FIG. 17;

FIG. 21 is a detail view taken along view C-4 of FIG. 17;

FIG. 22 is a plan view of a first course of the saferoom of FIG. 1;

FIG. 23 is a plan view of a second course of the saferoom of FIG. 1;

FIG. 24 is a detailed perspective view showing a roof truss rod configuration according to an exemplary embodiment of the present invention;

FIG. 25 is a detailed perspective view of the roof of the saferoom of FIG. 1;

FIG. 26 is another detailed perspective view of the roof of the saferoom of FIG. 1;

FIG. 27 is a partially cutaway perspective view of the roof of the saferoom of FIG. 1;

FIG. 28 is another partially cutaway perspective view of the roof of the saferoom of FIG. 1;

FIG. 29 is a partially cutaway side view of a saferoom having a flat roof, according to another exemplary embodiment of the present invention;

FIG. 30 is a partially cutaway end view of the saferoom having a flat roof of FIG. 29;

FIG. 31 is a detailed view taken along view D-1 of FIG. 29;

FIG. 32 is a detailed view taken along view D-2 of FIG. 30;

FIG. 33 shows a front view of a base plate used under each building corner, where the shape and hole location can be determined by overlapping centroid of tension rod triangle with centroid of concrete anchor triangle, so uplift reaction is perfectly centered and plumb;

FIG. 34 is a perspective view of a hip bracket disposed at each corner of the building, aligned by centroids of reaction in the corners, similar to the base plate of FIG. 33;

FIG. 35 is a right side view of the hip bracket of FIG. 34;

FIG. 36 is a front view of the hip bracket of FIG. 34;

FIG. 37 is a top view of the hip bracket of FIG. 34;

FIG. 38 is a side view of a wall section C-channel design according to an exemplary embodiment of the present invention;

FIG. 39 is a side view of a wall section—transverse to door, according to an exemplary embodiment of the present invention;

FIG. 40 is a top view showing show brackets used in a 12-foot building structure;

FIG. 41 is a front view of the 12-foot building structure of FIG. 40;

FIG. 42 is a top view showing show brackets used in a 14-foot building structure;

FIG. 43 is a front view of the 14-foot building structure of FIG. 43;

FIG. 44 is a top view showing show brackets used in a 16-foot building structure;

FIG. 45 is a front view of the 16-foot building structure of FIG. 44;

FIG. 46 is a top view of a butt joint formed along a wall, according to an exemplary embodiment of the present invention; and

FIG. 47 is an end view of a wall member showing offset spine channels for creating the butt joint shown in FIG. 46.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Broadly, an embodiment of the present invention provides a saferoom/tornado shelter that is made primarily of wood and includes walls that can withstand missile impact testing as recommended under FEMA P-320/P-361. The saferooms of the present invention can be designed for a single family or small business, or can be designed as a larger community shelter. The wood wall can accommodate various architectural finish treatments and enhancements much more easily than a concrete or steel building saferoom.

The wall assembly described herein can serve as the protective exterior wall portion of a FEMA P-320/P-361 saferoom (tornado shelter) and also comply with tenets of the ICC-500 building code which governs the construction of these buildings. The requirements for these compliances are at least twofold: 1) the assembly must pass the debris missile impact test as described in the code, and 2) the assembly must also meet engineering requirements established for these structures by NSSA, FEMA, and the ICC, and guided by ASTM engineering standards for loads and reactions. The specific protocols for wall and roof performance may be accessed at the website of the Wind Science and Engineering Dept. at Texas Tech University (TTU) where these ideas were first developed.

The wall assembly of the present invention is currently the only wall design executed in natural wood which meets these requirements.

The industry which serves the need for above-ground shelters has been exclusively served by the manufacture of steel and concrete products (one Kevlar unit has been made) which, while they serve the intended purpose of “near perfect life safety” protection during extreme weather events, do not lend themselves as a multi-purpose or living space usage due to their size and other design and material constraints.

The wood wall herein described provides not only flexibility in size and shape, but accommodates a wide variety of architectural finish treatments and enhancements, all the while yielding at least R-11 insulating values without cladding or added materials.

Another advantage of the wall assembly of the present invention is the utilization of a fast-growing, sustainably harvested natural wood material, Southern Yellow Pine, preserved with copper azole and kiln dried afterward as the primary structural element. Carbon sequestration and lowered carbon footprint are thus achieved in a type of building formerly restricted too much higher carbon-embodied construction materials such as concrete and steel. While some concrete and steel are indeed required in a completed structure of the design of the present invention, the embodied carbon load reduction is significant. While Southern Yellow Pine is described as a wood product for the wall assembly of the present invention, other wood products may be used within the scope of the present invention.

The wall assembly of the present invention has been tested at TTU and approved. FIGS. 3 through 7 show some testing results for missile impact. While not being limited to any particular theory, the performance of the wall assembly of the present invention derives from the development of a wall with differentially pressured planes, that is, the establishment of a high pressure zone located toward the back (inside) of the assembly, and a zone of pressure relief toward the outer, or impact face of the wall. Further contributing to the “designed imbalance” of the wall is an offset and “loose” spline arrangement in the low pressure plane, which achieves missile energy dissipation by development of a “crush zone.” Tests show that the “crush zone” disperses remaining missile energy, after fiber shearing has occurred, in an upward and downward direction in the plane of the outer wall face. This redirection of energy effectively prevents damage to, or displacement of, the inner face of the wall.

This result specifically meets the “no spalling” requirement of ICC-500, and the wall assembly of the present invention has even received testing approval from the Wind Science and Engineering Research Lab at TTU for safe application of sheetrock to the inner wall, indicating a high degree of “shock absorption” as well as overall protection.

A saferoom 10 can be formed from four walls 12 and a roof 14. Typically, a door 16 can be disposed in one of the walls. Optional windows can also be formed in one or more of the walls. The walls 12 can be formed from stacked lumber 18, having channels 20 cut along their lengths, with an outer channel 22 cut proximate to an outside of the wall on one face of each piece of lumber, and an inner channel 24 cut near a center of the width of the other face of each piece of lumber. Typically, both the inner channel 24 and the outer channel 22 are formed on an outer half of the lumber. In other words, if a line is drawn down the middle of the width of the lumber, both channels 22, 24 would be on the same side of this line, and, during construction of the building, these channels 22, 24 would be aligned on the outside of the building. Splines 26 can be disposed inside the channels 22, 24. Typically, the channels 22, 24 are from about ⅜ to about ½ inch deep and from about ¾ to about 1 inch wide. The splines 26 can be about ¾ inch square, thereby fitting into channels 22, 24 when the lumber is stacked.

If the wall has a length that requires pieces of lumber to be butt together, as shown in FIG. 46, a steel tubing member 50 can replace at least a portion of the spline 26. Typically, the steel tubing member 50 is from about 4 inches to about 3 feet long and may be disposed equally into each of the abutting pieces of lumber.

A plate, such as a steel plate 28 can be disposed on a top side of the wall. A truss rod 30 can be disposed through a hole 32 formed through each of the pieces of lumber 18 forming the wall. The hole 32 is formed in an interior half of the lumber 18, proximate to an inside surface 34 of the wall. A tensioning nut 36 can be disposed on the end of the truss rod 30 to provide pressure downward against the lumber 18 forming the wall 12. This wall design has been found to meet various impact, wind and projectile tests.

With overlapped and notched corners (see FIGS. 22 and 23), the wall is constructed of flat stacked layers in a unique orientation, and is assembled without nails, screws, glue, or fasteners of any sort, excepting the tensioned high-strength steel rods positioned through holes bored in the back third of each member. A notch 40 on a first wall can meet with the end of a lumber piece of an adjacent wall. In the next course (FIG. 23), the adjacent wall member has the notch 42, and the first wall meets into this notch 42. Precise rod tension can be measured and maintained using various methods, such as direct tension indicating washers, for example. This tension permits the frictional coefficient of the wood members to overcome the wall and total building “racking” load produced during extreme wind events, without cross bracing or other conventional building elements. The tension rods can be spaced at even intervals so as to establish “modularity” in engineering and testing, thus allowing use in a variety of building configurations.

The tension rods pass through a “top-plate” of steel, where this steel plate induces pressure on the wood member below, but primarily only in the pressure zone (rear portion) of the wall, as a relief cut in the top wood member disallows direct pressure on the front portion of the wall. There is, of course, some pressure applied laterally by each wood member on the member below in the outer plane of the wall, but the wood grain orientation limits this pressure, and allows “controlled splitting” along the grain at missile impact, whereupon the wall's front face measure may increase slightly.

Each wood member has spline channels cut longitudinally and offset top-to-bottom, to accept positioning and shear load sharing splines, but only in the low pressure plane (front portion) of the wall.

The wood splines can be placed unfastened and can be vertically undersized to allow displacement upward and downward, but tightly fitted in the direction of their width, that is, perpendicular to missile impact, so as to achieve shear load sharing between layers upon impact.

The entire wall assembly of the present invention thus achieves a “plate” effect in the high tension zone, and is anchored from the tension rods to an ICC-500 compliant foundation with approved anchors.

The wall top-plate, as a component of the overall building, can be overlapped and bolted with high strength bolts to produce a “compression ring” effect, which allows a roof structure (described below) to bear upon it without lower chords (ceiling joists or trusses) and hence allows an open, or clear span, interior space.

The wall assembly of the present invention can be used to assemble a saferoom that meets the debris impact guidelines of FEMA P-320/P-361 and ICC-500. Various roof designs may be used with the wall assembly of the present invention to provide the saferoom. Exemplary roof designs are described below, but other roof designs may be contemplated within the scope of the present invention.

The purpose of the roof assembly described herein is to serve as the protective roof portion of a FEMA P-320/P-361 saferoom (tornado shelter) and also comply with tenets of the ICC-500 building code which governs the construction of these buildings.

The requirements for these compliances are at least twofold: 1) The assembly must pass the tornado debris missile impact test as described in the code, and 2) must also meet engineering requirements established for these structures by NSSA, FEMA, and the ICC, and guided by ASTM engineering standards for loads and reactions. The specific protocols for wall and roof performance may be accessed at the website of the Wind Science and Engineering Dept. at Texas Tech University where these ideas were first developed.

The wood roof panels herein described provides not only flexibility in size and shape, but accommodates a wide variety of architectural finish treatments and enhancements, all the while yielding at least R-8 insulating values without cladding or added materials.

Another advantage of the roof assembly of the present invention is the utilization of a fast-growing, sustainably harvested natural wood material, Southern Yellow Pine, preserved with copper azole and kiln dried afterward as the primary structural element. Carbon sequestration and lowered carbon footprint are thus achieved in a type of building formerly restricted too much higher carbon-embodied construction materials such as concrete and steel. While some concrete and steel are indeed required in a completed structure of this design, the embodied carbon load reduction is significant. While Southern Yellow Pine is described as a wood product for the wall assembly of the present invention, other wood products may be used within the scope of the present invention.

The roof assembly of the present invention has been tested at TTU and approved. While not being limited to any particular theory, the performance of the roof assembly of the present invention derives from the invention of a roof with differentially pressured planes, that is, the establishment of a high pressure zone located toward the back (inside) of the assembly, and a thin plywood non-pressure layer toward the outer, or impact, face of the roof. The “designed imbalance” of the roof is less than that of the associated wall, as described above, but nonetheless achieves the missile impact requirements at the lowered speed for a roof under 30 degrees pitch.

This result specifically meets the “no spalling” requirement of ICC-500, and this assembly has even received testing approval from Wind Science and Engineering Research Lab at TTU for safe application of timber framing elements to the inner ceiling, indicating a high degree of “shock absorption” as well as overall protection.

The roof assembly (see FIGS. 8-13 and FIGS. 24-28, for example) can be constructed of a framework of steel I-beams with wide flanges which can be in-filled with specially designed wood panels as herein described. The panels can include two layers—an outer plywood layer (for example, ¾ inch plywood) which is loosely fastened (not in tension or compression), and an assembly of SYP timbers which are stacked in layers and placed in compression by high-strength steel tension rods, the precise tension being measured and monitored by various mechanisms, such as be direct tension indicator washers. Offset wood splines achieve both positioning and shear load sharing between members.

These roof assemblies achieve positive connection to the steel beams by virtue of extension of the tensioning rods through holes in the I-beam webs, and subsequent fastening with nuts and washers (non-dti type).

The roof panels can be capped on the fascia, or lower roof-edge side, with a full width steel plate which flange-bolts to the beams, thus further locking the panels into the beams.

The pyramidal hip roof associated with the saferoom as herein describes can use a central connecting hub to properly orient, assemble, and secure the steel wide flange I-beams which form the supporting skeleton of the roof assembly.

This hub is referred to as an “oculus” even though the pictured embodiment has a solid steel lower face, as an optional embodiment of such hub would permit the transmission of natural light, as occurs in the design of classical buildings such as cathedrals. The difficulty of achieving this direct form of lighting in a storm shelter/saferoom is evidenced by the fact that only a single product, specially designed by one manufacturer, has been able to demonstrate sufficient resistance to debris missile impacts, as well as other criteria required of glazing products, and was only approved for such use in December, 2011 for use in FEMA 361 saferooms.

The oculus can be used in stabilizing the linear roof elements, the “transverse and diagonal ribs (or hip ribs)”, against both uplift and downward loads exerted on the roof at this central connecting region at the roof peak. The oculus may otherwise be manifest as a curved ring (classical oculus), faceted polygon, or other shape depending on overall building design. The current embodiment is a square with twelve connecting flanges, specific to this hip-roofed construction.

As shown in FIG. 38, a section of steel C-channel, legs upward, which is about 20″ long and which ties the transverse rafter to two truss rods in the middle of the wall. This C-channel can be repositioned to sit directly over the truss rods in the rear portion of the wall. As shown in FIGS. 40-45, a “shoe bracket” for door openings and also for windows is shown. The same I-beam frame can be used, going all the way to the concrete for windows (as for doors). The windows can be in-filled below with a wood wall section according to the present invention, with an additional cross brace to complete the window frame (beneath the window). In other words, one basic frame design can be used for both door and window, with the window being in-filled below. The unusual “legs” below the window can be covered with, for example trim and planter box frill.

In practical terms, the rigidity of the oculus allows it to be used as an aid to assembly of the roof structure. When the oculus is securely positioned and braced in the appropriate space, the ribs of the vault may be attached and bolted at their upper and lower ends with ease and precision. The steel frame may thus be assembled in place on the building, piece by piece, without subassembly or additional bracing.

The oculus may also serve as an extra portal for ventilation, when covered by an approved missile shield for FEMA P-320/P-361 structures, and when the finished roof detailing (shingles or the like, not shown, applied by others) complies with code approved building practice for roof vents.

The oculus design of the present invention as shown has been approved under FEMA P-320/P-361 and ICC-500 to withstand missile impact with or without the vent shield, and is designed to resist the loads imposed on the roofs of such saferooms.

An exemplary connection between the roof and the wall is shown in FIGS. 9 and 12. An exemplary connection between the roof and the oculus is shown in FIGS. 10 and 11. A door and window opening design is exemplified in FIGS. 9/20 and 13/21, respectively. FIGS. 14 and 15 show various ground connections, such as those used about the building perimeter and those used on sides of an opening, such as a door.

FIG. 22 shows a plan view of “course 1” of the saferoom design. While multiple steel channel hold down brackets are shown inside the building, formed from each truss rod, the number of channel hold down brackets can vary depending on design and to be appropriate to support the saferoom on its foundation.

FIGS. 22 and 23 show a corner alternating overlap design. The design from FIGS. 22 and 23 can alternate as the building is constructed and each wood layer is placed.

As shown in FIGS. 30-32, another embodiment of the roof panels is their application to flat roof assemblies. Here the panels would be rectangular in shape.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. 

What is claimed is:
 1. A wall assembly comprising: a plurality pieces of lumber having a length, a width and a thickness, the plurality pieces of lumber stacked atop each other to form a wall height equal to a sum of the thickness of each of the plurality of pieces of lumber; a first channel formed along the length of the lumber, the first channel formed in a first side of the lumber proximate to an outer surface of the wall; a second channel formed along the length of the lumber, the second channel formed in a second, opposite side of the lumber proximate a central region of the lumber, wherein the first and second channels of one of the plurality of pieces of lumber aligns with the first and second channels of an adjacent one of the plurality pieces of lumber; first and second spline members fitting into the first and second channels; a top plate on a top edge of the wall; a truss rod fitting through the top plate, passing through the wall, and secured to a floor plate, wherein the truss rod fits through the wall proximate an inner surface of the wall; and a tensioning device disposed at an end of the truss rod, the tensioning device operable to apply tension on the top plate and the plurality of pieces of lumber disposed therebelow.
 2. The wall assembly of claim 1, wherein the tensioning device is a tensioning nut.
 3. The wall assembly of claim 1, wherein a first wall assembly meets a second wall assembly at a corner, wherein notches are formed in the plurality of pieces of lumber at the corner.
 4. The wall assembly of claim 3, wherein one of the plurality of pieces of lumber of the first wall assembly has the notch formed therein to receive one of the plurality of pieces of lumber of the second wall assembly, and an adjacent one of the plurality of pieces of lumber of the second wall assembly has the notch formed therein to receive an adjacent one of the plurality pieces of lumber of the first wall assembly.
 5. The wall assembly of claim 1, wherein the floor plate is secured to a layer of concrete.
 6. The wall assembly of claim 1, wherein the plurality of pieces of lumber are dimensional lumber.
 7. The wall assembly of claim 1, further comprising a steel tubing member disposed in at least one of the first and second channels at a butt joint of two pieces of lumber along the wall assembly.
 8. The wall assembly of claim 7, wherein the steel tubing extends from about 4 inches to about 3 feet.
 9. A saferoom comprising: a roof; and a plurality of walls, each of the plurality of walls comprising: a plurality pieces of lumber having a length, a width and a thickness, the plurality pieces of lumber stacked atop each other to form a wall height equal to a sum of the thickness of each of the plurality of pieces of lumber; a first channel formed along the length of the lumber, the first channel formed in a first side of the lumber proximate to an outer surface of the wall; a second channel formed along the length of the lumber, the second channel formed in a second, opposite side of the lumber proximate a central region of the lumber, wherein the first and second channels of one of the plurality of pieces of lumber aligns with the first and second channels of an adjacent one of the plurality pieces of lumber; first and second spline members fitting into the first and second channels; a top plate on a top edge of the wall; a truss rod fitting through the top plate, passing through the wall, and secured to a floor plate, wherein the truss rod fits through the wall proximate an inner surface of the wall; and a tensioning device disposed at an end of the truss rod, the tensioning device operable to apply tension on the top plate and the plurality of pieces of lumber disposed therebelow.
 10. The saferoom of claim 9, wherein the tensioning device is a tensioning nut.
 11. The saferoom of claim 9, wherein a first wall assembly meets a second wall assembly at a corner, wherein notches are formed in the plurality of pieces of lumber at the corner.
 12. The saferoom of claim 11, wherein one of the plurality of pieces of lumber of the first wall assembly has the notch formed therein to receive one of the plurality of pieces of lumber of the second wall assembly, and an adjacent one of the plurality of pieces of lumber of the second wall assembly has the notch formed therein to receive an adjacent one of the plurality pieces of lumber of the first wall assembly.
 13. The saferoom of claim 9, wherein the floor plate is secured to a layer of concrete.
 14. The saferoom of claim 9, wherein the plurality of pieces of lumber are dimensional lumber.
 15. The saferoom of claim 9, further comprising a steel tubing member disposed in at least one of the first and second channels at a butt joint of two pieces of lumber along the wall assembly.
 16. The saferoom of claim 15, wherein the steel tubing extends from about 4 inches to about 3 feet. 